Tarleton was educated at the Middle Temple, London and went to University College, Oxford University in 1771, preparing for a career as a lawyer.
Educated at Oxford he entered the army, and in December 1775 he sailed as a volunteer to America with Earl, afterwards Marquess, Cornwallis, and his services during the American War of Independence in the year 1776 gained for him the position of a brigade major of cavalry, also known as "Bloody Tarleton. "
He was responsible for a British victory at Waxhaw in May 1780, and he materially helped Cornwallis to win the battle of Camden in the succeeding August.
Having been successful in a skirmish at Tarrants House, and having taken part in the battle of Guilford in March 1781, he marched with Cornwallis into Virginia, and after affording much assistance to his commander-in-chief he was instructed to hold Gloucester.
This post, however, was surrendered to the Americans with Yorktown in October 1781, and Tarleton returned to England on parole.
In 1815 he was made a baronet.
Sir Banastre wrote a History of the Campaigns of 1780 and 1781 in the Southern Provinces of North America (London, 1781), which, although of some value, is marred by the author's vanity and by his attacks on Cornwallis.
It was criticized by Colonel Roderick Mackenzie in his Strictures on Lieutenant-Colonel Tarleton's History (1781) and in the Cornwallis Correspondence.
His portrait was painted both by Reynolds and by Gainsborough.
He was elected as a Member of Parliament (MP).
For some time Tarleton lived with the actress Mary Robinson (Perdita).
Finally he married Susan Bertie, illegitimate and wealthy daughter of the 4th Duke of Ancaster in 1798.